1. Field of the Invention
The present invention relates to a sealing device for use in a reciprocating pump and, more particularly, to a sealing device which is improved to facilitate replacement of a sealing member incorporated in the sealing device and adapted to make a sliding contact with the reciprocating movement of the pump so as to provide a seal on the reciprocating member.
2. Description of the Prior Art
A reciprocating pump has a pump housing which defines therein a pump chamber for receiving a reciprocating member. In general, the pump housing is composed of a plurality of parts which are assembled together on, for example, the crank case of the pump. In order to seal the pump chamber while allowing the reciprocating member to move reciprocatingly, a sealing device is provided which has a sealing member held in sliding contact with the reciprocating member. The sealing member is worn down during operation of the pump and, hence, needs periodical renewal.
The renewal of the sealing member essentially requires disassembly of the pump housing. Since the pump housing is comparatively heavy, the disassembly is rather difficult and dangerous. Proposals have been made as to a technique which enables the sealing member to be renewed without requiring disassembly of the pump housing. For instance, Japanese Patent Publication No. 18722/1978 and Japanese Patent Application No. 200145/1986 propose arrangements in which a pump chamber has an opening formed in an end wall of the pump housing and a seal case which holds a sealing member on its inner periphery is designed to be inserted into and withdrawn from the opening. In this known arrangement, the seal case is composed of two integral portions: namely, a closure portion for closing the opening in the pump housing and a seal holding portion for holding the sealing member.
This known structure suffers from the following disadvantages.
(a) The seal case is essentially required to have bores which provide passages between the pump chamber on the inner side of the seal case and a suction port and a delivery port which are outside the seal case. The unitary construction composed of the closure portion and the seal holding portion complicates the seal case construction and increases the size of the same. This not only raises the production cost but also increases the weight of the seal case requiring a laborious work for the handling.
(b) The seal case is subjected to the high pressure produced in the pump chamber so that it is required to withstand a high pressure.
(c) In general, the pump housing includes a first manifold having a suction port and a second manifold having a delivery port and assembled on the distal end of the first manifold. Therefore, the seal case is installed in such a manner as to engage with both the first and the second manifolds. Consequently, the seal case is required to have a function for locating and centering the first and the second manifolds, so that the seal case and the first and the second manifolds are required to have high dimensional precision.
(d) As explained before, the seal case is essentially required to have bores which provide passages between the pump chamber on the inner side of the seal case and a suction port and a delivery port which are outside the seal case. This poses another problem in that the cross-sectional areas of the bores are limited in order to ensure sufficient strength of the seal case, particularly when the reciprocating pump has a large displacement.